Problems with PowerPoint 2011 for Mac

Hey guys one quick question. I have to use Microsoft PowerPoint 2011 on my MacBook Pro 13" for school and there is a big problem. I cannot change the spelling language.

It's a version I downloaded from my University Website. The spelling only gets checked for English, but I often write texts in German so I have to change the spell checking. I have Word 2011 from my University too (the whole Office came in one packet) and there I was able to change the spelling language without any problems.